This invention relates generally to flip-flop circuits, and more particularly to a flip-flop circuit which comprises a plurality of MOS field effect transistors (abbreviated hereinafter as MOSFET's) and resistors and which is featured by a small drive power requirement, small power consumption and reliable transition between an on state and an off state.
Prior art flip-flop circuits and typically composed of, for example, bipolar transistors and resistors or MOSFET's and resistors as described at pages 134 to 135 of a book entitled "Shusekikairo no Kaiseki to Sekkei" (Analysis and Design of Integrated Circuits) published on Apr. 1, 1969 by Kindai Kagakusha Publishing Company in Japan. Such flip-flop circuits are widely used for memories and logic elements of modern electronic circuits and for driving switching elements of modern electronic circuits.
FIG. 1 shows a basic form of a prior art, flip-flop circuit composed of bipolar transistors and resistors. A flip-flop circuit can be formed by an interconnection of a pair of logic circuits, and in the structure shown in FIG. 1, a first bipolar transistor 20 and a second bipolar transistor 21 are interconnected. The interconnected first and second transistors 20 and 21 cannot simultaneously take their on or off state. When the first transistor 20 is in its on state, an "L" level appears at a first output terminal O.sub.1, while an "H" level appears at a second output terminal O.sub.2. When a pulse signal is applied to a second input terminal IN.sub.2 in the above state of the circuit, the collector-emitter voltage of a fourth transistor 22 decreases to turn off the first transistor 20, and the second transistor 21 is turned on in turn. Accordingly, an "H" level appears at the first output terminal O.sub.1, while an "L" level appears at the second output terminal O.sub.2. An inverse operation to that described above occurs when a pulse signal is then applied to a first input terminal IN.sub.1. Thus, the states of the output terminals O.sub.1 and O.sub.2 can be inverted by application of a pulse signal to the input terminal IN.sub.1 or IN.sub.2. However, the prior art flip-flop circuit shown in FIG. 1 has the following problems:
(1) The power consumption of the flip-flop circuit itself is large due to a continuous flow of current through either the transistor 20 or 21. PA1 (2) Large drive power is required since bipolar transistors are used to form the flip-flop circuit. PA1 (3) The signal--receiving transistor 19 or 22 requires large drive power in order to cause the transition of one of the interconnected transistors 20 and 21 from its on state to its off state.
In FIG. 1, reference numerals 23 and 24 designate resistors for connecting the transistors 20 and 21 to power supply terminals V.sub.1 and V.sub.2 respectively.